Cooled, high-frequency electric cable



Sept. 27, 1949.

w. M. ROBERDS 2,483,301

COOLED, HIGH-FREQUENCY ELECTRIC CABLE Filed Oct. 31, 1944 C010 10/7752//0. f/TFMF INVENTOR.

ZZ/[flg/ 7724 0057125 irme/w-y Patented Sept. 27, 1949 COOLED,HIGH-FREQUENCY ELECTRIC CABLE Wesley M. Roberds, Collingswood, N. Jasslgnor to Radio Corporation of America, a corporation of DelawareApplication October 31, 1944, Serial No. 561,270

8 Claims. (Ci- 174-15) This invention relates to electric cables, andmore particularly to a cable which is especially suitable for use withhigh frequency induction heating apparatus, although by no means limitedto such use.

In high frequency induction heating apparatus, it has been founddesirable to cool not only the inductor coupling coil by means of whichheating energy is applied to the work, but also the leads or conductorswhich connect the coupling coil to the source of highfrequency energy.In many cases, it has also been found extremely desirable to provideflexible leads for connection of the coupling coil to theenergy source.It has been customary to provide leads between the coupling coil and theenergy source in the form of a cable. So far as I am aware, no suchcable has been provided heretofore which is both flexible and can besuitably cooled.

The primary object of my present invention is to provide an improvedelectric cable suitable for use with high frequency induction heatingapparatus, which cable is both flexible and can be readily cooled.

More particularly, it is an object of my present invention to provide acable as aforesaid which can be manipulated easily and without strain onthe operator where the cable is to be used with a hand operatedapplicator.

Another object of my present invention is to provide an improvedelectric cable as aforesaid which is quite simple in construction,economical incost, and highly efllcient in use.

In accordance with my present invention, I provide a pair ofelectrically conductive bands or strips together with an insulatingstrip therebetween and place these strips inside of a flexible, rubbertube which constitutes a conduit or sheathing. The rubber tube ispreferably, although not necessarily, substantially circular in crosssection and the aforesaid conductive and insulating strips extendsubstantially diametrically thereacross, being preferably of a widthjust slightly less than the internal diameter of the tubing. Thus, theconductive strips are spaced from the adjoining wall portions of thesheathing, and suitable end plugs or closures at each end of thesheathing aiford electrical connection to the conductive strips and arearranged to admit a coolant at one end of the tube and to discharge thesame at the other end, the coolant passing through the spaces betweenthe conductive strips and the sheathing. If desired, the conductive andinsulating strips may be formed with aligned passages which affordcommunication between the two spaces on opposite sides of the conductivestrips. This permits circulation of the coolant around the conductivestrips while passing through the conduit to enhance cooling.

The novel features that I consider characteristic of my invention areset forth with particularity in the appended claims. The inventionitself, however, both as to its organization and method of operation, aswell as additional objects and advantages thereof, will best beunderstood from the following description of one embodiment thereof whenread in connection with the accompanying drawing, in which Figure 1 is acentral, longitudinal, sectional view of one form of electric cableconstructed in accordance with my present invention,

Figure 2 is an enlarged, sectional view taken on the line 11-11 of Fig.1,

Figure 3 is an enlarged, sectional view taken on the line III-Ill ofFig. 1, and

Figure 4 is a fragmentary, detail, perspective view of one of theconductive strips utilized in my novel cable.

Referring more particularly to the drawing, wherein similar referencecharacters designate corresponding parts throughout, there is shown aflexible, rubber tube l of circular or substantially circular crosssection having a pair of funnel-like terminal members 3 and 5 connectedto the ends thereof. The members 3 and 5 are made of Bakelite or othersuitable insulating material and are closed off, respectively, bycooperating closure members I, I and 9, 9. The closure members 1, I and8, 9 may be comprised of split cylinders of copper or other suitable,electrically conductive material.

Within the sheathing I and end members 3 and I are a pair of conductivestrips or bands II and II which extend along the entire length of thesheathing (as seen in Fig. 1) and substantially diametricallythereacross (as best seen in Fig. 3). The conductive strips II and I!are thus spaced from the adjoining wall portions I a and lb of theconduit or sheathing I to provide spaces I I and I1 through whichcooling water, air, or other suitable coolant may be passed. Theconductive strips II and I3, like the sheathing I, are flexible and areformed with offset loops Ila and Ila, the termini of which haveelectrical connection with the closures I and 9. A strip ll of suitableinsulating material is interposed between the closure members I, I, theconductive strips II and I3, and the closure members 9, 9.

thereby insulating the two sets of conductors from each other. Like theconductors ii and ii, the strip i9 extends diametrically across thesheathing i and may be of the same width as the strips H and IS.

The closure members or blocks 1, 'i are provided with openings throughwhich extend conductive tubular members 2i, the bores in the tubes 2icommunicating with the passages i and i1 through suitable openings inthe conductive strips ii and it, such as the openings lib shown in Fig.4. A suitable coolant, such as cold water, may be supplied to the tubes2i and the spaces i5 and i1 through a Y-connector 23. The tubularmembers 2i may also serve as a means of external connection of the cableto a suitable source of high frequency electrical energy, such as aradio frequency oscillation generator (not shown), through a couplingtransformer 24.

A pair of conductive, tubular members which extend through the closureblocks 9, 9 also have communication with the spaces i5 and IT and mayserve as discharge tubes for the cooling fluid after it has passedthrough spaces i5 and ii. The conductive members 25 may be connected toan inductor coupling coil 21 or other suitable applicator in anyconvenient manner, and the applicator or coil 21 may be provided with anoutlet 29 through which the cooling fluid may be discharged. If desired,a Y-connector similar to the connector 23 may be connected to the tubes25 for discharging the cooling fluid, and the conductive members 25 maybe connected to a suitable work or utilization circuit in a mannersimilar to the connection of the intake tubes 2i to .the transformer 24.

From the foregoing description, it will be apparent to those skilled inthe art that I have provided an improved cable which is both flexible,by reason of the flexibility of the sheathing i, the conductors ii andi3 and the insulating strip i9, and which can be cooled effectively inthe interest of efilciency. To further increase the efllciency ofcooling, the conductive strips ii and i3 and the insulating strip l9 maybe provided with a series of aligned notches or the like ll, 33 and 39,respectively, in longitudinally spaced relation along both edges thereofto provide passages through which communication is established betweenthe spaces i5 and [1, as clearly shown in Fig. 3.

Although I have shown and described but one embodiment of my presentinvention, it will undoubtediy be apparent to those skilled in the artthat many other forms thereof, as well as variations in the particularone described, are possible. For example, the strips ii, l3 and i! mayhave a fairly tight flt in the sheathing i so as to substantially blockoff the spaces i5 and i! from each other and the tubular members 25 maybe omitted, in which case the cooling fluid will be admitted through oneof the tubes 2i to pass through one of the spaces i5 and H to the otherend of the cable, thence to the other space through suitable openings inthe strips ii, i3 and II, and flnaliy discharged through the other tube2i. Furthermore, the sheathing or conduit i may be made of othermaterial than rubber which has suitable flexibility and electricalinsulating properties, particularly for high power work. It will also beapparent, no doubt, that my improved cable may be used with other thaninduction heating apparatus, as, for example, in apparatus used forheating dielectric materials by reason of dielectric losses producedtherein. Other uses are also possible. I, therefore, desire that myinvention shall not be limited except insofar as is made necessary bythe prior art and by the spirit of the appended claims.

I claim as my invention:

1. An electric cable comprising a hollow sheathing of insulatingmaterial, a pair of electrical conductors in said sheathing extending.along the length thereof in spaced relation to each other, a pair offunnel-like terminal members of insulating material respectivelyconnected into the ends of said sheathing, a pair of electricallyconductive closure members inserted in each of said funnel-like membersand closing the interior thereof oil from the exterior, electricalinsulating means interposed and extending between said conductors andbetween the two clocure members of each pair for insulating saidconductors and the two closures of each pair from each other, one ofsaid conductors having electrical connection with two of said closuremembers, one at each end of said cable, the other of said conductorshaving electrical connection with the other two of said closure members,one at each end of said cable, means, extending through each of theclosure members at one end of said cable and communicating with thespace between said conductors and the sheathing wall, for admitting acooling fluid to said space, and means, extending through each of theclosure members at the other end of said cable and also communicatingwith said space, for discharging said cooling fluid.

2. An electric cable according to claim 1 characterized in that themeans connected to the 010-- sure members at said one end of said cablefor admitting said cooling fluid is constituted by a pair ofelectrically conductive tubes each having electrical connection with aseparate one of said pair of closure members, said tubes being adaptedto serve as a means of external connection of said cable to a source ofelectrical energy.

3. An electric cable according to claim 1 characterized in that themeans connected to the closure members at said other end of said cablefor discharging said cooling fluid is constituted by a pair ofelectrically conductive tubes each having electrical connection with aseparate one of said closure members, said tubes being adapted to serveas a means of external connection for said cable.

4. An electric cable comprising a hollow, flexible sheathing ofinsulating material, said sheathing being substantially circular incross section, a pair of conductive strips in said sheathing extendingalong the length thereof and substan tially diametrically thereacrosswhereby to provide spaces between each of said strips and the adjoiningwall portions of said sheathing, a strip of insulating materialinterposed between said conductive strips for electrically insulatingsaid conductive strips from each other, a pair of closure membersconnected to said sheathing at each end and closing the interior thereofoff from the exterior, and means for admitting a cooling fluid into saidspaces, and providing end connections for said conductive strips throughsaid closure members, said conductive and insulating strips being allformed with aligned passages affording communication between saidspaces.

5. An electric cable according to claim 4 characterized in that saidconductive strips and said insulating strip are all formed with alignednotches in their respective edges at longitudinally spaced pointsthereon to provide said passages.

6. An electric cable comprising a sheathing constituted of a flexibletube of insulating material,

a pair of electrically conductive, flexible strips in said sheathingextending along the length thereof in spaced relation to each other, apair of electrlcally conductive closure members connected to saidsheathing at each end and closing the interior thereof oil from theexterior, a strip of electrical insulating material interposed betweensaid conductive strips and between the two closure members of each pairthereof for insulating said conductive strips and the two closuremembers of each pair from each other, said insulating strip being alsoflexible, one of said conductive strips having electrical connectionwith two of said closure members, one at each end of said cable, theother of said conductive strips having electrical connection with theother two oi said closure members, one at each end of said cable, meansextending through the two closure members at one end of said cable andcommunicating with the space between said conductors and the sheathingwall for admittingza cooling fluid to said space, and means extendingthrough the two closure members at the other end of said cable and alsocommunicatin with said space for discharging said coolingfluid.

7. An electric cable according to claim 6 characterized in that saidconductive strips are formed with loops at their respective ends, saidconductive strips being electrically connected to their respectivelyassociated closure members at substantially the termini of said loops.

8. An electric cable according to claim 6 characterized in that saidsheathing is substantially circular in cross section, and characterizedfurther in that conductive and insulating strips extend substantiallydiametrically across said sheathing.

WESLEY M. ROBERDS.

REFERENCES crrEp The following references are of record in the his 0!this patent:

UNITED STATES PATENTS

